Field of the Invention
The present invention is in the technical field of implanted medical devices. More particularly, the present invention relates to a multi-directional locking mechanism that can be incorporated in any kind of implant device that needs to be fastened to a bone, including fractured bones and bones that are not fractured. For example, the multi-directional locking mechanism can be incorporated into fixation systems for bones of all types which use plates and screws and other implants such as prostheses that are affixed to bones with screws. Such fixation systems are used in osteosynthesis (bone fusion), wherein bone screws are connected to a bone and a plate which bridges the fracture. It is desirable for optimal alignment onto the bone fragments, or for compensating target errors, to be able to incorporate the bone screws at different angles into the plate.
The Related Art
Implants of various types may be indicated for the entire skeleton. Implants include bone plates, intramedullary nails, suture anchors and prostheses of various types including joint prostheses and elements thereof such as acetabular cups for hip replacement prostheses. A “bone fixation device” may include any of a variety of devices that secure an object to a bone, including but not limited to bone screws, pins, blades and the like.
The present invention seeks to remedy the problems of the prior art. The invention provides a multi-directional locking mechanism in the fastener hole (also referred to herein as a “hole” or “passage hole” or “through hole”) of an implant, without the need for additional components, that can accommodate conventional locking screws in a plurality of angles in a stable manner. The invention allows, for example, the overall thickness of a bone plate to be minimal providing for a low profile locking plate. Unlike the prior art, the invention is not required to rely on cross threading, gouging or stripping of the fastener hole threads and the bone screw threads. Also, the invention may create negative space around the periphery of the fastener hole to accommodate displaced material when the screw head engages features of the fastener hole to create a locked condition. This space may be created by a beam member (sometimes referred to herein as a “beam”) that is connected to the body of the implant. The space and beam configuration can be any geometry or combination of geometries as will be apparent to those having skill in the art based upon the disclosures herein. At least one space and one beam member should advantageously be present. The negative space may allow the beam member to translate both parallel and perpendicular to the axis of the passage hole. Because the beam member is thin, the movement of the beam member along its length may vary. All of these degrees of freedom may be beneficial to accommodate a wide variety of implants.